Vibrating screen



Dec. l, 1959 w. E. sAxE 2,915,183

VIBRATING SCREEN Filed July 6, 1954 4 sheets-sheet 1 WALTER E'. SAXE,

INVENTOR.

HUEBNER, aEEf/L En, won/m. a Hmz/c,

By! D DATTRNEVSZ l, 1959 w. E. sAxE VIBRATING SCREEN 4 Sheets-Sheet 2Filed July 6. 1954 vlm i AT WW.

WALTER E. SAXE, INVENTOR.

HUEBNER, BEEHL El?,

WOR/PEL HERZ/G,

Dec. l, 1959 w. E. sAXE 2,915,183

VIBRATING SCREEN Filed July 6, 1954 4 Sheets-Sheet 25 ff; fia fa; fff

f?? figa? j?! WALTER E. SAXE',

IN VEN TOR.

HuEs/vEmaEEf/L En, Wonne/ a HERZ/c, By U ATTORNEKSZ Dec. 1, 1959 w. E.sAxE 42,915,183

VIBRATING SCREEN Filed July 6, 1954 4 Sheets-Sheet 4 j. Iyl

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' AHORA/Em Mika United States Patent O The invention relates to poweroperated screens and has particular reference torelatively large screensfor commercial use which are vibrated in order to advance the aggregateover the screen and wherein the vibrating mechanism is adapted toadjustment in order to acconimodate diierent types of aggregate anddiierent conditions.

The application is a continuation-impart of co-pend ing applicationSerial No. 296,374, led June 30, l952,

now Patent No. 2,707,559, issued May 3, 1955.

Although attempts have been mare heretofore to provide screening deviceswhich are power operated, where attempts have been made to shakethescreen by use of power, the mechanism has been extremely inadequate tomeet varying c onditions for screens of diferent types. Movement of aiixed type has apparently been considered sutlicient and little or noattention has been given to providing a means of adjusting the movementor shaking effect to produce a versatile machine with relatively littleapplication of force. Further still, where agitation has been resortedto, attempts to advance the larger particles screened out by the processto a location where in a continuous process they can be discharged fromthe screen have not been satisfactory.

It is therefore an object of 'this invention to provide controlledvibration at approximately right angles to the screening medium inpreference to what may be termed circular vibration, which circularvibration wastes a large portion of the operation in motion which onlydisturbs the screening action by striking the material particlessideways instead of moving directly at them to produce a more orderlyand controlled advance of the material over the screen. i i, .i

lt is further among the objects of the invention to provide a new andimproved power operated screen so constructed that it can handlerelatively heavy loads at a continuous rate and further so constructedthat the material being screened is steadily and gradually advancedtoward a discharge end of the screen in order that the screening surfacemay be kept clear of larger particles which are screened out.

Another object of the invention is to provide a vibrating screen whereinthe application of vibrating force is in a plane tilted with respect tohorizontal so that particles screened out are advanced from a loadingend of the screen to a discharge end of the screen either by reason ofthe tilt o f the screen, by reason of the application oi the vibratingforce, or a combination of both. e

Still another object of the invention is to provide a new and improvedpower vibrated screen device wherein l`the application .of vibratingpower to a screening surface is in such variety that e number ofindividual screens cell be mounted in vseries so that aggregate to bescreened after beine passeduover one screen ceu be dischargedupon-successive. screens ,in e continuous Process With'vibretionsadjusted to the `screen size thereby to divide ou,t Particles ot .astent ,runny .ditlerent sizes by use of screens of diierent mesh one inseries with the next.

2,915,183 VEatented Dec. l, 1959 ICC Still another object of theinvention is, to provide a` vibrating elementfor articles in the natureof vibrating screens so constructed that weight in the olf-,center porttion of the vibrating elementcan be changedwhile the, opertaion is inprogress so as to change the vibrating characteristics of the off-centermechanism without it being necessary to make mechanical or physicaladjustments in those portions of the device. e

Still further among the objects of the invention is to provide forvibrating different portions of thel screen atl different rates as, forexample, by changing the speed of rotation o f ythe vibrator as well asadjusting the vi-V bretor physically, thereby to produce differentvibrational characteristics in the saine screen et ,dilerent stages olthe screening process,

Further still anions the objects of vthe invention is to provide amovable mounting means for securing a vibrat-l ing screen to astationary support which will readily p er` mit application ot .evariety of, vibrational characteristics to the 'screen While .at theseine time -firmly holding the ,screen in its location upon the supportWith these and other objects. in view, the invention consists in theconstruction, arrangement and combina; tion of the various, parts of thedevice whereby the .objects contemplated are attained, as hereinafterslet forth, pointed out in the appended claims .and illustrated in theaccompanying drawings.

In the drawings:

Figure 1 is a plan view of one form of the device ilmlostrating theinvention.

Figure 2 is a side elevational view of the screen shown in Figure 1.

Figure 3 is a partial cross-sectional view taken on the line 3-3 ofFigure 2.

Figure 4 is a crossfsectional view through one of the vibrating elementspartially broken away teken on. the line 4-4 of Figure 2. v v a Figure 5is a fragmentary longitudinal sectionalview on the line 5-5 of Figure 4l Figure 6 is a planview of a multiple drive arrange,- ment showing ascreen o f extra length in ycombination With e multiple vibratorrnechenistnv Figure 7 4is aside elevational view :of the screen of.Figure 6.

Figure 8 is a plan view of still another forrn'of the device. a e

Figure 9 .is a side elevational view .of the device .shown in Figure r8.i

Figure 10 is a plan view partially kbroken away showing still anotherform of the device.

Figure ll is aside elevational view ofthe device shown in Figure 10.

Figure 12 is av plan view of still another form ofthe invention showingweights located onall sides of the screen.

Figure 1,3 is a side` elevational view on the line 13-13 of Figure l2.

In the form of the device illustrated in Figures 1 to 4, inclusive,there is shown a pair etk supportingchannels 10 and 11 resting uponS9111@ permanent stationary surface 12 to which they may besecured byappropriate conf ventional means,.not shown. A screen frame indicatedgenerally by the'reference character 13 is mounted upon the supportingchannels in a horizontal plane. The screen frame -consists of framechannels 14 and 15 forming the llongitudinal sides of the screen frame."l`hese'chan-` nels are secured together byl cross beams 16 and ,117,

suitably welded in place. The rectangular screen frame i upturned rigidflange 21 on the screen is engaged by the hooked member 19. On theopposite side of the screen a similar upturned'flange 22 is adjustablysecured by means of a screw hook 23 held in the upstanding leg of anangle bar 24, this bar in turn being fastened to the channel 15. By thismeans the screen may be firmly stretched over the top of the screenframe.

In order to resiliently support the screen frame upon the supportingchannels and 11, there are provided a series of rods or columns 2S oneach side. Each rod has an eyelet 26 at the top'adapted to receive abolt 27, thereby to pivotally secure the eyelet to a boss 28 in turnfastened to the channel 14 or 15, as the case may be. Similar means isused to secure the bottom end of each rod 25 to the appropriatesupporting channel as, for example, an eyelet 29' secured by a bolt 29.The rods and their securing bolts are in a parallelogram arrangement, asclearly shown in Figure 2, so that thevscreen frame is free to raise andlower, dependingl upon its resilient support, and as it raises or lowersit maintains itself in a horizontal plane.

To secure the screen frame in elevated position, there is provided anupstanding bracket 30 secured to the supporting channel 11 by means of abolt 31. A downwardly extending bracket 32 is secured at the upper endof the bracket to the lower flange of the frame channel 14 or 15, as thecase may be, by welding or other appropriate means. As noted there is apair of the brackets 30, 32 on each side of the frame. The brackets havefree ends locatedopposite each otherin spaced relation, as indicatedparticularly in Figure 2. A bolt 34 extends through the lower end of thebracket 32 and thence over the distance between the bracket andthroughthe upper end of the bracket 30. A spring is interposed betweenthe bracket 30 and a nut 36 and surrounds the bolt. By providing adevice as just described on each side of the frame, the frame -is heldin elevated position from which position it can be vibrated upwardlyagainst the compression of the spring 35 as the operation proceeds.

To provide motive power properly located to vibrate the screen apedestal 37 is mounted upon the stationary surface 12 at the upper endof which is a platform 38 supporting a motor 39. From the motor a beltdrive 40 is connected to a pulley 41 keyed upon a shaft 42.

yThe shaft in turn is rotatably mounted upon bearing brackets 43, 44, 45and 46 secured to the cross beam 17 of the frame.

At each end of the shaft 42 is a bevel gear 47 meshing with a similarbevel gear 48 on a shaft 49. The shaft 49 in turn is mounted uponbracket 50 which is secured to the respective frame channel and 51secured to the lower end of the bracket 32. The shaft 49 is mounted inan oblique direction substantially parallel to the direction of the rods25 and slightly oblique relative to the axis of the bolt 34.

` Non-rotatably mountedV on the shaft 49 is a hollow cylindrical housing52 shown in detail in Figures 4 and 5.

The cylindrical housing is mounted off-center upon the shaft. Inside ofthe housing is a pair of eccentric weights 53 and 54 located, as shownin Figure 4, so as to provide a space or chamber 55 therebetween. rl`heshaft 49 is a tubular shaft and has a block 56 therein through whichpasses a pipe 57 centrally disposed within the shaft 49. The pipeprotrudes through the block and has a right angularly bent portion 58extending radially outwardly of the housing S2 and centerably disposedwithin the charnber 55. The portion 58 of the pipe terminates near aninner wall 59 of the housing 52. Although the eccentric weights 53, 54provide for the vibration of the shaft and consequently the screen, thevibration characteristic can be altered by varying the quantity of aliquid 60 in the chamber 55, the chamber being closed as indicated by aplate 61. The pipe 57 may be connected by suitable means, not shown, toa source of the liquid 60 and additional liquid passed into the chamber55 for the achievement of certain vibrational characteristics where aheavier weight might be needed or withdrawn from the chamber for othervibrational characteristics where a lighter weight might be needed.

When the screen of Figures l, 2 and 3 is set in vibration by operationof the motor 39, the direction of application of the vibrating force isin an angular direction toward the right from vertical as viewed inFigure 2, this because of the direction of mounting of the shaft 49. Theforce imparted by the vibration is at the left end of the screen, asviewed in Figure 2. When aggregate is loaded at this end of the screen,which may be considered as the loading end, the aggregate will bebounced step by step toward the right, during which time the lineraggregate falls through the screen and the coarser aggregate whichcannot pass the screen gradually passes to the right end of the screenwhere it can be projected oi the screen to be collected by a suitablelreceptacle, not shown, beneath the right end of the screen. Thevibrational characteristics of the vibrator may be varied to suitdifferent types of aggregate placed on the screen or perhaps differentkinds of screenings which it may be desired to collect.

In a second form of the invention illustrated in Figures 6 and 7 thereis shown a single long screen 70. The screen is supported at the cornersof each by means of a rod 72 extending upwardly to a link 73 which inturn passes through a beam support 74 at the upper end of which is aspring housing 75 having a spring 76 therein. The link 73 is attached tothe spring at its upper end so that the spring acts in compression toresiliently support the respective corner of the screen 70. Intermediatesupports may also be used. It should be noted that an eyelet 77 is usedto connect the rod 72 to the screen, the eyelet connection being similarto the connection between the rod and the link 73 suicient that there bea certain freedom of motion at these points.

The screen in turn comprises frame channels 7S and 79 having beams 81 atthe opposite ends, one of which is shown in Figure 6, whereby tocomplete the frame construction. Screen Wire 82 is stretched over theframeand secured in the same manner as described in connection withFigures l, 2 and 3. It will further be noted that the frame and screenwire thereon occupies a position in a horizontal plane in the case ofFigures 6 and 7.

For imparting vibration to the screen at different locations along itslength there is provided a shaft 83 rotatably mounted one on each sideof one end of the screen by means of bearing brackets 84, 85 and 86.There is an appreciable obliqueness or slope to the mounting of theshaft 83 in each case. Vibration is produced by the presence ofeccentric weights 87 and 88 non-rotatably secured to the shaft 83.Effective vibration is achieved when the weights 87 at the upper ends ofthe shaft 83 have their off-center weighted portions extending inopposite directions when the weighted portions are in the same plane. Tothis end the weighted portions will both be directed upwardly at thesame time and downwardly at the same time, therebyy to act together. Inside positions such as that shown in Figure 6, they counter-balance eachother so that there is no sideward thrust or vibration imparted to thescreen.

To provide for rotation of the'shaft 83, power is taken from a suitablesource and transferred through a belt drive 89 to a pulley 90non-rotatably mounted upon a shaft 91. The shaft in turn is rotatablymounted by means of brackets 92, 93, 94 and 95 to the frame and inparticular to the cross-beam 81. A bevel gear 96 is located at each endof the shaft 91, meshing with a similar bevel gear 97 at the upper endof the shaft 83. By this train of power, shafts 83 on opposite sides ofthe frame are rotated at the same rate of speed and simultaneously withrespect to the weights 87. The tilted direction of the shaft 83 effectsan application of vibrational force an `oblique direction toward theright, as

viewed in Figures 6 and 7. This tiltedor oblique application ofvibrating force tends to advance thev heavier particles which do notpass through themesh of the screen in periodic jumps from the left endof the screen toward the right end of the screen as the liner particlesare sifted or screened through. Hence the left end of the machine may bedesignated as the loadingend.

To secure a continuous operation and in order to screen out allparticles of the various different size which comprise the aggregate,minimizing waste dumped oithe discharge end, the screen may be madevirtually any desired length, as illustrated.

To continue the application of power from the vibrating portion of theleft end of the screen to the right end of the screen, a sprocket 98 ismounted atthe lower end of the shaft 83 and has a chain 99 extendingthereover toy a sprocket 100 at the upper end of the shaft 83 of thescreen 71. When the sprockets 98 and 100 are made of the same diameterand number of teeth, rotation of the shafts 83 on the left and rightends of the screen, respectively, will be at the same rate of speed.Obviously, ifvthe screen be extra long, it is further possible to addstill a third vibrating mechanism, not shown, in exactly the samefashion as already described. The process may thus be extended to anyreasonably desirable length without varying structure from that shownand described. So long as the application of the vibrational effect isin an oblique direction, particles not screened through the mesh of thescreen will continue to advance toward the right until discharged olfthe discharge end of the screen.

In still a third form of the device illustrated in Figures 8 and 9 thereis provided a tilted support105 comprising channels 106, the upper endof each of which is mounted upon a column 107 and the lower end ofeachrof which is mounted upon a pivot ange 108. The column and the pivotange in turn are bolted to a suitable stationary surface 109. Forconvenience in adjusting the slope of the support the column 107 may beprovided with a series of holes 110 through which a bolt 111 may bepassed in order to secure the upper end of the channel 106 on each sidein any one of the different positions indicated by the holes.

A screen 112 of the form of the invention of Figures 8 and 9 isconstructed in a fashion similar to the screens heretofore described inthat they comprise a frame of side channels 113 secured together bytransverse beams 11,4, one at each end. A wire mesh 115 is stretchedacross the upper edges o f4 the frame to provide the screening element.

In the case of Figures 8 and 9 compression springs 116 mounted in pairssupport each corner of the frame of the screen, the springs being heldby suitable keepers. To more securely anchor the frame upon thesupporting channels, there is provided on each side a tension rod 117pivotally secured at the left end by means of an eyelet 118 in turnattached to a bracket 119 at the upper or left-hand end of the channel106 by use of a bolt 120. At the right-hand end of the tension rod 117an eyelet 121 is secured to a bracket 122 by means of a bolt 123. Thetension rod thus mounted tends to hold the screen in the position shownin Figure 9 to the extent that as the screen is vibrated transverselyrelative to the plane of its mounting, it will not tend to be urgedtoward the right. Freedom of motion up and down permitted by the springs116 is not impaired.

To vibrate the screen there is provided a motor support 124 upon whichis mounted a motor 125 operating a belt drive 126 to rotate a pulley1217 in turn keyed to a shaft 128 rotatably mounted upon brackets 1219,130, 131 and 132 on the cross-beam 114. Bevel gears 133 and 134 transferthe rotational eect to shafts 135, one on each side of the frame. Theshafts are secured by appropriate brackets 136 to the channel 113 of theframe, the shafts in turn being in a plane parallel to the plane of themesh 115 and parallel to each other. Eccentric weights 137 arenon-rotatably secured to the shaft `on each side and these eccentricweightsimparta vibrational eifectfup and down to the screen when theshafts 135 are rotated, rotation being as show at the same rate ofspeed. 1

Because of 'the sloping disposition of the screen frame and screen,` theelect of the vibration imparted to the screen is to lift the particlesofaggregate placed at the upper end of the screen upwardly in a directionnormal to the surface of the screen. After the apex of the lift curvehas been reached, the particles will fall straight down by action ofgravity, to a position lower down `on the screen and thus step by steptraverse the length of the screen until the particles notscreenedxthrough the mesh willV fall from the lower or discharge end ofthe screen. Therefore, although the shafts'carrying the eccentricweights are mounted parallel to the plane of the screen, neverthelessthe effect of vibration imparted to the screen by the eccentric weightson the shaft tends to advance the aggregate from a loading end towardadis? charge end, while the finer screened* aggregate passes through thescreen.

vIn still another formv of. the invention illustratedV in Figures 1 0and 11 there is shown a screen 140 mounted horizontally. The screenis'constructed of two channels 141 suspended at each end by a suspensionrod 142 ex.- tending into a spring housing 143 on a stationary support144 in a manner similarr to themounting described in detail inconnection with Figure 7. The mounting referred to provides a resilientsupport at each of the four corners of the screen. Transverse beams 145complete the frame structure.

iIn this form of the device there is a shaft 146' rotatably secured tothe frame at the left end by means .of brackets y147'. A similar shaft148 is securedv to the-right end by means of brackets 149. The bracketsin each case are suitably bolted to the lowermost flange ofthe channel141 on each respective side of the frame. Shafts 146 and.148 areparallelto each other and parallel to the horizontal plane in which the screen140 is mounted. Wire mesh 150 is attached over the frame in the samemanner as previously described in connection with the rst and succeeding forms of the invention. On each of the shafts 146 and 148 is aneccentric weight 151 shown centerably disposed in the form of theinvention selected for the i purpose of illustration.

To elfect rotation of the shafts 146 and 148 there is provided a motor152 secured to a stationary surface 153 by suitable bolts. The motor isequipped with sprockets 154 and 154' non-rotatably mounted upon a, motorshaft 155. A chain 156 transfers rotational motion from the sprocket 154to a sprocket 157 non-rotatably mounted upon the adjacent endof theshaft 146. A similar chain 158 transfers rotational motionfrom thesprocket 154 to a sprocket 159 mounted upon an idler shaft 160. Alsomounted upon the idler shaft is a gear 161 meshing with `a gear 16,2 ofthe same diameter. The idler shaftr in turn is mounted for rotation on asuitable idler bracket 163 on the underside of the respective channely141 at the right end of each. The weights 151 maybe made different if itbe desired to vibrate one end of the screen differently from the other.l

lIn the form of `the device illustrated in Figures l2 and 13 vibrationis applied at each of four sides of a rectangu lar ,screen assembly 170.The screen assembly is suspended at each of four corners by -a rod 171mounted on a beam 172 through an appropriate resilient support 173. Inthis form a motor 174 mounted with its drive sprocket, 175 parallel tothe vplane of the screen rotates a master driven shaft 176 by means of achain 177 and sprocket 178. Bearing brackets 179 support the shaft onthe screen assembly. Side shafts 180 and 181 are secured to the screenassembly by brackets 182. In each instance a bevel gear 183 carried bythe respective shaft is driven by a corresponding bevel gear 184 on themaster driven shaft 176. A shaft 185 secured to the 7 screen assembly bybrackets 186 is driven by bevel gears 187 and 188 from thefshaft 181.Each of the shafts has an eccentric weight 189 fixed thereon with theweighted side so located that the weights oppose and balance each otherin all directions except the vertical direction, regardless of wherealong the respective shafts the weights may be set. Hence there will beeffective vibrationin a direction perpendicular to the plane of thescreen and vibration in this direction will be facilitated by theresilient mountings in the supports 173.

There has accordingly been described herein certain vibrationalcharacteristics and screens having certain inherent vibrational designssuch that whether mounted horizontally or tilted the vibration providesfor a progress of unscreened aggregate from the loading end to thedischarge end, which progress is continuous until the unscreenedaggregate is discharged. The screens are so devsigned with respect totheir vibrational portions that the vibrating effects may be varied to acertain extent. Moreover, by reason of the design and location of thevibrational portions of the devices, the screens in many cases may beplaced end to end so that should a screen of the usual length not besu'lcient to perform the necessary operation, it may be extended to asufficient length on the same frame without the necessity of providingtransfer points and thus effect an efficient continuous operation.

While I have herein shown and described my invention in what I haveconceived to be the most practical and preferred embodiment, it isrecognized that departures may be made therefrom within the scope of myinvention, which is not to be limited to the details disclosed hereinbut is to be accorded the full scope of the claims so as to embrace anyand all equivalent devices.

Having described my invention, what I claim as new and desire to secureby Letters Patent is:

1. A vibrating screen device comprising a support, a horizontal framehaving a screen thereon, a plurality of obliquely extending parallelrods on each side of the screen pivotally connected at ends thereof tothe frame and the support, a resilient supporting connection on eachside of the screen extending transversely to the axial direction of saidcolumns, a shaft rotatably mounted on each side of the frame at an anglesubstantially parallel to the axes of said rods, a weight on eachshaft'extending off-center in a direction opposite fromvthe weight onthe shaft opposite thereto when reaching laterally extended positions, arotating source of power on the support and a flexible power train fromsaid source to said shaft adapted to rotate said shaft simultaneously atthe same speed. Y

2. A vibrating screen device comprising a support, a horizontal framehaving a screen thereon, a plurality of obliquely extending parallelcolumns on each side pivotally connected at ends thereof to the frameand the support, a pair of brackets on each side of the frame, onebracket of each pair comprising an upwardly extending bracket on thesupport and the other bracket of each pair comprising a bracket on theframe extending downwardly and laterally spaced from said first bracket,a resilient connection between each pair of brackets and extendingtransversely to the axial direction of said columns whereby toyieldingly fix the location of said frame, a pair of spaced obliquelyextending bearings on each side of the frame having axes thereofsubstantially parallel to the column, and a shaft rotatably mounted ineach pair of bearings at an angle substantially parallel to the axes ofsaid columns, a weight on each shaft extending olf-center in ardirectionopposite from the weight on the shaft opposite thereto when reacingmaximum outer and inner rotative positions, a rotating` source of poweron the support and a-flexible power train from said source to saidshafty adapted to rotate said shaft simultaneously at the same speedwhereby to concentrate the vibration impulses in the screen and isolatedfrom the support.

3. A vibrating device comprising a tubular shaft, and an eccentricdevice non-rotatably secured to the shaft, said eccentric devicecomprising a closed hollow housing mounted eccentrically on the shaftand forming a chamber, and a pipe centrally mounted in the tubular shaftand having an open end extending radially outwardly from the shaft andin said chamber to the outer portion thereof and comprising means forchanging the quantity of liquid in said chamber whereby to vary thevibration characteristics of the device.

4. A vibrating screen device comprising a tubular shaft rotatablymounted on the screen device, and an eccentric device non-rotatablysecured to the shaft, said eccentric device comprising a closed hollowhousing mounted eccentrically on the shaft and forming a liquidreceiving chamber on one side only of said rod, a liquid partiallyfilling said chamber, and a pipe mounted in the tubular shaft ononefside only of said shaft and having an open end extending radiallyoutwardly in said chamber to the outer portion thereof and comprisingmeans for adding to andsubtracting from the quantity of liquid in saidchamber whereby to vary the vibration characteristics of the screendevice.

5. A vibrating screen device comprising a support, a screen frame havinga plurality of separate resilient connections between opposite sides ofthe frame and the support, tubular shafts rotatably mounted on oppositesides of the frame in an oblique position relative to a horizontalplane, and an eccentric device non-rotatably secured to each shaft, saideccentric device comprising a closed hollow cylindrical housing mountedeccentrically on the shaft and forming a chamber, eccentric weightelements partially lling opposite sides of the chamber` and forming aspace therebetween on one side only of the shaft, a liquid partiallyfilling said chamber a pipe centrally mounted in the tubular shaft andhaving an open end extending radially outwardly in said chamber to theouter portion thereof and comprising means for adding to and subtractingfrom the total quantity of liquid in said chamber whereby to vary thevibration characteristics of the screen device.

References Cited in the file of this patent UNITED STATES PATENTS1,185,611 Dougan May 30, 1916 1,363,495 Cottrell Dec. 28, 1920 2,200,724Robins May 14, 1940 2,304,573 Kessler Dec. 8, 1942 2,353,492 OConnorJuly 11, 1944 2,367,070 Symons Ian. 9, 1945 2,596,281 OBrien May 13,1952 2,597,503 Larsson May 20, 1952 2,634,617 Dryg Apr. 14, 19532,707,559 Saxe May 3, 1955 2,722,840 Kececioglu Nov. 8, 1955 FOREIGNPATENTS 854,007 Germany Oct. 30, 1952 722,218 Great Britain Jan. 19,1955

